1. Field of the Invention
The present invention generally relates to apparatuses and methods for recording information and apparatuses and methods for reproducing information. The present invention particularly relates to an information recording apparatus and method which add or write (in an overwriting manner) binary or multilevel data to an information recording medium such as an optical disk, and also relates to an information reproducing apparatus and method which reproduce the recorded information.
2. Description of the Related Art
When information needs to be recorded on a certain type of information recording medium, the information may be recorded in a concatenated manner such as to follow the existing information recorded on the previous occasion. Technology for recording information in such a concatenated manner includes the following examples.
The “concatenated data recording/reproducing method and apparatus” of Patent Document 1 discloses a method of adding, or writing in an overwriting manner, data to an optical disk. In the case of DVD-RW, data up to the 16-th byte of the first frame of the first sector is recorded with respect to an ECC block that serves as a unit of recording. When concatenated recording is required, provision is made to start concatenated recording at the 15 to 17-th byte of the first frame of the first sector.
The “information recording medium recording method” of Patent Document 2 discloses a method of adding, or writing in an overwriting manner, data to an optical disk. When concatenated recording is required, provision is made to start concatenated recording at the 1 to 3-rd byte of the third frame of the first sector. In the case of concatenated recording for DVD-R, provision is made to start concatenated recording at the 82 to 87-th byte of the second frame of the first sector.
The “recordable information recording medium, read-only information recording medium, and method of preventing illegal copying” of Patent Document 3 discloses preventing illegal copying by recording data in units of one ECC block, by arranging linking areas comprised of two sync frames at the boundaries between ECC blocks, and by forming a line of emboss pits as asperities in advance in the linking areas.
The “information recording apparatus, information recording method, information recording medium, and information reproducing apparatus” of Patent Document 4 discloses recording data in units of one ECC block and providing a linking area comprised of two sync frames at the boundaries between ECC blocks.
The “information recording medium” of Patent Document 5 discloses recording data in units of one ECC block and providing a linking area comprised of one sync frame at the boundaries between ECC blocks. In this linking area, a special pattern called “VFO” is recorded in order to stabilize the operation of the data reproduction system (PLL circuit).
With regard to multilevel recording, Non-Patent Document 1, for example, discloses signal processing performed at the time of recording/reproducing multilevel data as a technology for improving recording density. In order to increase the storage capacity of an optical disk, the multilevel recording of 0 to 7 (8 levels) is performed in contrast with the conventional binary recording of 0 and 1. When multilevel data is to be recorded, 11 bits of binary data are modulated into four 8-level data items for recording as shown on P. 39 and FIG. 12, for example.    [Patent Document 1] Japanese Patent Application Publication No. 2002-83466    [Patent Document 2] Japanese Patent No. 3367657    [Patent Document 3] Japanese Patent Application Publication No. 2002-260339    [Patent Document 4] Japanese Patent Application Publication No. 2002-260341    [Patent Document 5] Japanese Patent Application Publication No. 2003-59206    [Non-Patent Document 1] Ricoh Technical Report No. 28 P. 34-P. 41
In the case of Patent Document 1 and 2, a predetermined location within an ECC block is used as a concatenation point at which concatenated recording is performed. At the time of data reproduction, therefore, data for approximately two frames (one horizontal line in the ECC block) following the concatenation point is not properly reproduced, resulting in error data. In the ECC block that includes the concatenation point, data preceding the concatenation point is recorded on the previous occasion, and has nothing to do with the data following the concatenation point. When error correction is performed in this ECC block, thus, the data preceding the concatenation point ends up being treated as error data. Accordingly, in an ECC block that includes a concatenation point, a large amount of error data is generated over the area extending from the start of the block to the end of the two frames following the concatenation point.
In the case of Patent Documents 3, 4, and 5, dedicated linking areas are provided as additions at the boundaries between ECC blocks. This gives rise to a problem in that recording capacity is reduced.
Non-Patent Document 1 discloses a modulation method for recording multilevel data and a demodulation method for reproducing the multilevel data for the purpose of improving recording density. There is no teaching of a data structure usable for error correction. There is thus a problem in that a practical optical-disk system cannot be brought to fruition.
Accordingly, there is a need for scheme that can suppress data errors in an ECC block at the time of data reproduction without reducing recording capacity when information is added or written by concatenated recording to an information recording medium such as an optical disk.
Further, there is a need for the same scheme in the case of multilevel recording.